This invention relates to flip chip interconnection structures and, more particularly, to an interconnect structure formed by mechanical deformation and interlocking of asperities between the surfaces to be joined.
Flip chip interconnection between an integrated circuit (IC) chip and a substrate is commonly performed in electronic package assembly. In the most common form of such interconnection bumps on the IC chip are metallurgically joined to pads formed on the substrate, usually by melting of the bump material. While this approach provides robust connections, it is difficult to reduce the pitch of the interconnection due to the risk of bridging (i.e. shorting between adjacent connections) during the melting and solidification processes. In an alternative approach the attachment is made using a particulate film or paste, whereby conductive particles in the paste or film together with the shrinkage force of a resin effect an electrical connection. This approach lends itself to reduction of interconnection pitch but suffers from limited long term reliability owing to the susceptibility of the particulate interconnection to degrade over time.